1. Field of Invention
The present invention relates to a projector.
2. Description of Related Art
The related art includes projectors that are used for presentations at conferences, academic societies and exhibitions. Each of such projectors modulates and combines a light beam irradiated by a light source in accordance with image information and projects the light beam on a screen by a projection optical system in an enlarged manner.
In the above projector, there may be an occasion of projecting upward with the projector fixed at a lower level, or that of projecting downward with the projector fixed at a higher level. Related art document JP10-171044A, 3 to 4 pages, FIG. 2, discloses a projector, which is provided with a projection optical system position adjuster at an optical system such as an optical modulator etc. The projection optical system position adjuster moves a projection optical system in a direction orthogonal to a light-irradiating direction. The projection optical system position adjuster rotates a knob (rotary knob) left and right to drive as screwing the knob so as to move the projection optical system up and down.
However, in such a projection optical system position adjuster, since a rotary direction of the knob and a moving direction of the projection optical system are not correspondent, it is difficult to figure out whether the projection optical system is moved up or down, which is a first problem.
Further, in the projector equipped with the projection optical system position adjuster, an elongated opening through which a projection lens is exposed is formed at the projection optical system position adjuster and the casing where the projection lens is housed, so that the projection lens is moved along these elongated openings. In such projector, when the projection optical system is moved, a gap is generated between the projection optical system and the opening formed at the casing, thus the dusts etc. possibly being invaded from the gap. Additionally, the generated gap disfigures the projector. To close the gap, there is provided one or two shield plates which moves along with the projection lens on an inner side of the casing.
However, when the one or two shield plates follows the projection lens, the dimension of the casing along the moving direction of the projection lens must be long enough to secure a range where the shield plates move inside the casing. Accordingly, the length of the casing in the moving direction of the projection lens might be increased, thus increasing the size of the casing, which is a second problem.
Furthermore, when the two shield plates are used, a gap is generated at a part where the two shield plates are layered, and a light may leak from the gap, which is a third problem.